Multilayer Ceramic Capacitor Electrode Design for Thermal Stress
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Solution Overview
Problem
Multilayer ceramic capacitors experience cracking due to thermal stress and mechanical deformation when mounted on boards with different coefficients of thermal expansion, despite the use of metal terminals to absorb stress, as tensile stress in the plating film on the metal terminals can still cause cracking.
Innovation Solution
The design includes external electrodes with thicker peripheral portions on the end surfaces of the multilayer ceramic electronic components, connected by metal terminals with extended portions that create a gap between the component body and the mounting board, using phosphor bronze for improved heat conductivity and low electric resistance, to reduce tensile stress and enhance solder cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal terminals are provided to absorb stress, then the thermal shock resistance is improved, but tensile stress in the plating film causes cracking
Solution Approach 1:
The external electrode is designed with non-uniform thickness, featuring a thicker peripheral portion and a thinner center portion. This local quality variation allows the peripheral area to bear and distribute tensile stress away from the center, preventing stress concentration that would cause cracking while maintaining the metal terminal's stress absorption capability
Solution Approach 2:
The thickness parameter of the external electrode is changed from uniform to non-uniform distribution. By making the peripheral portion thicker than the center portion, the electrode's mechanical properties are optimized to resist tensile stress-induced cracking while preserving thermal shock resistance through the metal terminal
2Strength
If the external electrode thickness is increased to prevent cracking, then the stress resistance is improved, but the component size increases
Solution Approach 1:
Instead of uniformly increasing the external electrode thickness throughout, the design applies increased thickness only to the peripheral portion where stress concentration occurs. This localized thickening provides the necessary stress resistance while minimizing the overall volume increase of the component
Solution Approach 2:
The external electrode is functionally segmented into different thickness zones: a thicker peripheral portion for stress resistance and a thinner center portion for minimizing volume. This segmentation allows each region to serve its specific function optimally without compromising the other
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces the occurrence of cracking and improves the sealability and reliability of the multilayer ceramic electronic components by distributing stress and enhancing thermal management, while maintaining high moisture resistance and loading capacity.
Implementation Method 1
even when a stress due to temperature change or deformation of the mounting board occurs, it can be advantageously absorbed by the elastic deformation of the metal terminal
Implementation Method 2
using phosphor bronze for improved heat conductivity and low electric resistance
Data Source
AI summary
A multilayer ceramic electronic component includes an electronic component body including a laminate and an external electrode, and a pair of metal terminals that are joined by a joining material. The pair of metal terminals includes a terminal joint portion, an extended portion and a mounting portion. The external electrode is provided only on both end surfaces of the laminate, and includes first and second external electrodes. The first external electrode and the second external electrode each include a saddle portion with a thickness larger than the thickness of a center portion of each end surface in the periphery of the first end surface and the second end surface of the laminate, respectively.